“Basketball is a game of runs” means that there are periods when one team gets hot, but then cools off and the other team gets hot. The term “basketball is a game of spurts” dates to at least 1968 and “basketball is a game of runs” from at least 1985.
 
   
HoopSkills.com
Winning the Game of Runs
Analyze most every game at every level and you will notice that basketball is a game of scoring bursts, which are more commonly known as runs. It seems that both teams will often go along either trading buckets or defensive stops and play even for awhile until one of them eventually goes on a run and scores six or eight straight points.
 
9 December 1968, Cleveland (OH) Plain Dealer, “Late Spurt Wins for Royals, 120-115” by Bill Nichols, pg. 63, col. 2:
Basketball is a game of spurts and the 3,501 folks at the Arena saw a dandy spurt last nite.
   
5 February 1970, Oshkosh (WI) Advance-Titan, “Oshkosh holds off rally, down Indians, 79-77,” pg. 13, col. 3:
According to Titan basketball coach Bob White, “basketball is a game of spurts,” and that’s just what took place last Saturday night in the contest involving his cagers and LaCrosse as Oshkoshh defeated the Indians, 79-77.
 
8 February 1985, Chronicle-Telegram, “Grimy, grubby win just what Cavs needed” by Stever Herrick, pg. B6, col. 2:
“Basketball is a game of runs,” said Free, who led the Cavs with 29 points. “They made their run late. Fortunately for us, we made ours in the third quarter.”
 
Google News Archive
28 January 1986, Bulletin-Journal (Cape Girardeau, MO), “Indians secure key MIAA road win,” pg. 8B, col. 5:
“Basketball is a game of runs,” said Shumate.
(SEMO University Indians head coach Ron Shumate—ed.)
 
18 December 1989, Hutchinson (KS) News, “Struggling Tulsa shocks Oklahoma St. 95-80,” pg. 9, col. 2:
“As you all know, basketball is a game of runs and spurts,” Barnett said. “They got an 8-0 spurt and we’ve got to answer with our own spurt and we got it done.”
(Tulsa basketball coach J. D. Barnett—ed.)
     
20 February 1993, Marietta (GA) Daily Journal, pg. 5C, col. 1: 
“Basketball is a game of runs,” Ross said.
 
26 March 1993, Chicago (IL) Tribune, “Late run tops Cal” by Skip Myslenski, SPorts, pg. 3:
“Basketball is a game of runs,” said Cal coach Todd Bozeman. “You make one. They make one. You make one. The last one who makes one usually wins.”
 
Google Books
The Final Four
By Billy Reed and Rich Clarkson
Lexington, KY: Host Communications
2001
Pg. 168:
The Tar Heels had run off nine unanswered points. “Basketball is a game of runs,” Williams said.
 
Syracuse (NY) Post-Standard
Syracuse survives game of runs for 56-48 win over South Florida
Published: Wednesday, February 22, 2012, 10:48 PM   Updated: Thursday, February 23, 2012, 12:01 AM
By Mike Waters / The Post-Standard
(...)
“We were poised,’’ Jardine, who accounted for eight of SU’s 17 points in the first-half portion of the rally, said. “You have to be (poised) in that moment. Basketball’s a game of runs. At any given point, we were going to make our run.’’